Conventionally, various headphones are devised and are practically used. Among these headphones, a headphone for which a piezoelectric body is used as disclosed in Patent Literature 1 is also devised.
The headphone disclosed in Patent Literature 1 includes a band that allows the headphone to be attached to a head, and a speaker unit attached to both ends of the band and equipped with ear pads. In sound emission housing, speakers for which a piezoelectric ceramics plate is used are attached. By driving this piezoelectric ceramics plate according to a sound emission drive signal, sounds are emitted to eardrums of a user. Further, the speaker unit including the piezoelectric ceramics plate provides sounds to a user by way of bone conduction, too, by placing the headphone disclosed in Patent Literature 1 in contact with a bone via a user's skin.
PTL 1: Japanese Patent Application Laid-Open No. 2007-19957.
However, the headphone of Patent Literature 1 needs to cause sound emission and bone conduction vibration with respect to the eardrums by using one piezoelectric ceramics plate. Therefore, the piezoelectric ceramics plate becomes larger and heavier.
Further, when a shape of the piezoelectric ceramics plate becomes larger, the piezoelectric ceramics plate likely cracks upon vibration.
Furthermore, the headphone of Patent Literature 1 has a thick shape of the speaker unit since the ear pads of the speaker unit are filled with a fluid. Hence, even when the piezoelectric ceramics plate, which is supposed to be able to form the thin speaker unit is used, the speaker unit eventually becomes thick and large.